If you get a chance go over to Facebook and check out what is going on with the T1 Firebox Construction. It is very cool to see them making new parts at TVRM in Chattanooga. The boiler courses are being made in St. Louis right now and it looks like Firebox is being made in Chattanooga. These guys aren't messing around.

Jason Johnson, Gary Bensman and I along with a couple of local TVRM people flanged a sheet of 5/8" boiler plate into the rear tube sheet at the TVRM shop over a 3 day period. That was the first time I've ever experienced a McCabe flanger in action and I was very impressed.

I believe it is the second boiler course that is being formed in St. Louis.

From my recent interaction with the The T1 Trust. This is not a group of foamers with a dream. They are approaching this new build with serious professional analysis, followed by engineering design and resulting in the manufacture of parts. After what I saw this week, I have zero doubt that someday a T1 will be finished in this country.

In the photos, it seems to be that the tube sheet in question is that from the combustion chamber and not the smokebox, hence the sharp radius corners on one side. Through this it would appear that small amounts of work are being done to make the firebox.

Well, the tube sheet is certainly a start. The other more complex and expensive parts are the door sheet, backhead and throat sheets. When one or more of those are being made then we will know that a firebox is being constructed.

ekrwy2

Post subject: Re: PRR T1 Firebox Construction

Posted: Sat Mar 03, 2018 6:43 pm

Joined: Sat Jul 16, 2011 3:12 pmPosts: 81

I think this is terrific! I’m curious as to the stories of how slippery these machines were. Would lowering the boiler pressure help if that’s the case, similar to what the Frisco did with Russian decapods? (Rhetorical question for right now) I’m just excited I’ll get to see one in the next 15 or so years. Keep up the great work! Now what about a Timken 4 Aces... Just kidding.

_________________Bret Evanich

Jennie K

Post subject: Re: PRR T1 Firebox Construction

Posted: Sat Mar 03, 2018 9:55 pm

Joined: Fri Feb 13, 2015 2:48 pmPosts: 67

What has surfaced recently is that the engine crews were not properly instructed in the operation of the T1. They handled much differently than the K4 or the M1. They were just thrown in the cab and told to run them.

Overmod

Post subject: Re: PRR T1 Firebox Construction

Posted: Sun Mar 04, 2018 10:08 pm

Joined: Thu May 24, 2012 1:37 pmPosts: 972

There is much more to the slipping, including the fact that there are at least two distinct modes: high-speed and low-speed. The T1 Trust has engineering solutions to address both.

There has been quite a bit of documentation in the PRRT&HS Keystone over the years about truth vs. lies in the T1 story. One piece of information is that, net of all problems with the prototype locomotives, as late as April 1945 Paul Kiefer's postwar express locomotive design was a duplex, the C1a, with many of the same controlling dimensions as the PRR T1 (but, notably, with properly-sized piston valves, Baker gear, and a larger firebox -- almost the same boiler, in fact, being fitted to the 75" 4-8-4 prototype.) An interesting detail here was that, with the better economy of the duplex drive, 64T was thought to be adequate fuel to run Harmon-Chicago without stopping.

The low-speed slipping is not entirely soluble with 'better throttle technique' because the two engines on a T1 do not have separate throttles. It is remarkably difficult to tell when the front engine is slipping, and the only recourse with the stock arrangement is to close the air throttle and reopen it, which can make for some surge in train handling especially when the locomotive is negotiating low cross-level spots or crossovers, where unloading one driver might reduce the effective FA by a substantial part of 25% on that engine.

There is no room to fit two multiple poppet throttles in the space and header arrangement available, even if that were desirable. One proposed approach is to use Wagner throttles (as described briefly in the ACE 3000 patent) to 'trim' the steam flow to the forward engine independently of the main throttle; these are independent devices that do not interfere dramatically with the 'historic fabric' of the design. Another approach to low-speed slipping is to use a special modification of the independent-brake rigging on one or both engines that permits the same kind of fast application found in antilock braking, and also allows a certain amount of preload on the driver treads of either engine separately under poor traction conditions.

The high-speed slipping (as described, for example, by E.T.Harley) might not be a significant issue for 'normal' excursion service, but it becomes critical if the engine is to be run at high speed making best use of the advantages of the duplex principle. What happens is that at high speed, when the engine is making high relative horsepower via the poppet valves and exhaust tracting, a momentary loss of adhesion on one driver of four can make the engine momentarily start to break traction and spin up, far more readily than if you had eight drivers combined as on, say, N&W 611 at high cyclic rpm. In practice, this was somewhat self-limiting, but each time it occurs you get driver and railhead wear and stress on the running gear.

The 'ideal' solution is a modification of the conjugation proposed by Riley Deem for the Q-2 locomotive, which is to 'gear' the two engines together so they act like a 4-8-4 when necessary. I have determined that a better way to implement this is by using a Ferguson or magnetorheological clutch in the gear arrangement so that the gearing only passes significant torque when there is differential rotational speed between the engines, accommodating for example slight driver-diameter differences that for more rigid conjugation (e.g. the ACE 3000) would require frequent reprofiling and dressing of all the driver tires with an underfloor lathe arrangement. On 5550, which will have the external B-2 Franklin valve arrangement, it is relatively convenient to arrange this (in fact, there is already a lightening hole in the frame transom between the rear cylinders that is ideally placed) and so if high-speed slipping becomes a concern it will be fairly simple and direct to eliminate its poor effects, and not incidentally to allow the engine to be started and run at low speed as the equivalent of a four-cylinder 4-8-4 with 135-degree phasing thanks to detenting in the conjugation arrangement.

A secondary approach to high-speed slipping is to use a version of traction control, involving installation of cheek plates on some or all the driver centers and using lateral-acting air-over-hydraulic floating calipers as an independent brake. This at comparatively low cost allows perfect control, via computer if desired, over the effective rotation of both engines with very good angular resolution and if necessary heuristically-anticipatory response. As it has a remarkable effect on the appearance of the locomotive, this will not be installed on 5550 unless it turns out later to be needed, but it can very easily be applied and it will work.

_________________R.M.Ellsworth

484Mike

Post subject: Re: PRR T1 Firebox Construction

Posted: Mon Mar 05, 2018 8:35 am

Joined: Wed Mar 27, 2013 3:55 amPosts: 76

Hello Mr. chief designer ;-)

Which 75" 4-8-4 prototype are you referring to and where can I find further info on it?

Mike

hamster

Post subject: Re: PRR T1 Firebox Construction

Posted: Mon Mar 05, 2018 5:54 pm

Joined: Fri Jul 23, 2010 12:41 pmPosts: 406Location: Minneapolis, MN

I am sure that the T-1 Trust is absolutely aware of the "slippery" nature of this beast. Perhaps they are taking that into consideration in their engineering. Perhaps they are not. The ONLY group that has a say in this is the T-1 Trust. We can flog the dead horse as much as we want but such flogging is essentially foam. I suggest that we discuss performance in terms of what the original was and not in terms of what the reproduction MIGHT be. Suggesting engineering fixes or other corrections should be discouraged. We are not part of the engineering committee at the Trust.

The T-1 trust has not made public any of their engineering. Rather they seem to be letting the completed article speak for themselves. We have, so far, seen only a few of these and it is far too early to be making any conclusions.

whodom

Post subject: Re: PRR T1 Firebox Construction

Posted: Mon Mar 05, 2018 8:17 pm

Joined: Sun Aug 22, 2004 8:31 amPosts: 1120Location: South Carolina

484Mike wrote:

Hello Mr. chief designer ;-)

Which 75" 4-8-4 prototype are you referring to and where can I find further info on it?

Mike

I believe he’s referring to the NYC Niagara prototype, which was built with 75” drivers. These were later replaced with 79” drivers, and the subsequent production engines followed suit.

Per Hugh's comments, looking forward to the publication of "Know Thy Niagaras" by Tom Gerbracht via the NYCSHS, the deposit is in and looking forward to the material. It appears he will be addressing the proposed duplex in the book.

It would be interesting to see what design features which could be applied to the T1 without taking away from the spirit of the project.

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